U.S. Pat. No. 4,429,990, granted to E. J. Tamary, on Feb. 7, 1984, discloses a wicking structure for applying release liquid to a surface of a roller in a roller fixing apparatus. Release liquid, commonly referred to as "oil" is transported under pressure from a container to a permanent internal feed tube located inside a replaceable rotatable porous applicating wick. The wick constitutes a wicking or application roller which, when in contact with a fixing roller, is rotated by the fixing roller while it "oils" the surface. The structure has many advantages, including low cost, ease in articulation, and low wear on the fixing roller's surface. It also can be used on fixing belts or other moving surfaces.
The structure shown in that patent is commonly called a "rotating wick" and has been adopted commercially in a number of copiers and printers. The feed tube is cylindrical and has small holes laser drilled or punched along its elongated sidewalls through which liquid can pass. The wick is installed or pulled over the free end of the feed tube. The replaceable wick rotates either with respect to the feed tube or with the feed tube. It is a porous structure which includes an inner ceramic porous material that is covered by a porous and heat resistant fabric such as wool, or a comparable synthetic fabric. Such a synthetic fabric is marketed by DuPont under the trademark NOMEX (poly-(m-phenyleneisophthalamide)) and is a well-known capillary fabric which is resistant to heat and used for a variety of fusing system wicks. See also, U.S. Pat. No. 4,908,670 to Ndebi, issued Mar. 13, 1990; and U.S. Pat. No. 3,964,431 to Namiki, issued Jun., 1976.
The wool, NOMEX or other fabric wraps on virtually all prior commercial rotating wicks have worked well for many applications. However, for some applications, the fabric rolling with the fusing roller leaves a pattern defined by the fabric in the oil coating of the fusing roller. This can cause a pattern on the receiving sheet which is especially noticeable in transparencies. Low areas of oil can also cause insufficient release causing a pick-up of toner by the fusing roller. This, of course, disturbs the toner, the toned image on the sheet and in time causes wear to the fusing roller.
U.S. Pat. No. 5,043,768 issued Aug. 27, 1991 to S. C. Baruch; U.S. Pat. No. 4,942,433 to Stuart, issued Jul. 17, 1990, and U.S. Pat. No. 4,920,382 to Mills et al issued Apr. 24, 1990, discuss this problem at length and suggest solutions which are effective in certain environments.
The following references show stationary wicks having a needled wicking material such as NOMEX which spreads oil on a rotating roller. In some instances, the stationary NOMEX wick is covered by a porous Teflon to allow it to slide easier on the roller: U.S. Pat. No. 3,943,540, Vanderheyden, issued Mar. 9, 1976; U.S. Pat. No. 4,777,903, Wilcox, issued Oct. 18, 1988, U.S. Pat. No. 4,309,957, Swift, issued Jan. 12, 1982, U.S. Pat. No. 3,831,553, Thettu, issued Aug. 27, 1974, U.S. Pat. No. 4,426,953, Kromm, Jr. et al., issued Jan. 24, 1984, and U.S. Pat. No. 4,593,992, Yoshinaga et al, issued Jun. 10, 1986.